Using colony-born male stumptail monkeys (M. arctoides) we are studying the development of the cerebral cortical stellate and pyramidal cells during social rearing with graded amounts of sensory and/or motor deprivation. This year's study will extend previous work that concentrated on effects at 6 months of age to other age levels. Understanding cortical brain changes from birth to 2 years as functions of age and of environments and relating these to behavioral changes are the overall objectives. Physical growth, behavioral changes, and changes in dendritic development in sensory and motor areas of the brain are being investigated. Recovery or failrue to recover in terms of these developmental measures will be determined in animals that have been deprived for the initial 3 months after birth and then given social group rearing to 6 months. Drawings are made of stellate cells and pyramidal cells from specified layers of a given cortical area. Our previous studies of layer IV stellate cells will be extended to both stellate and pyramidal cells of layers II, III, and V.